1. Field of the Invention
This invention relates generally to an operating device for a gas circuit breaker used in a substation or the like in order to shut off the flow of abnormal current or accidental current, and more particularly, to an operating device of the type at such operable high speed that a time period from the start of the breaking or opening operation of an operating piston to the end of the reclosing operation of the operating piston is about 100 to 150 ms.
2. Description of the Prior Art
One conventional operating device for a gas circuit breaker is disclosed in Japanese Patent Unexamined Publication, No. 54-101168, with the operating device comprising an operating cylinder having an exhaust port at a predetermined position, an operating piston reciprocably movable along the operating cylinder at the time of the breaking (opening) and closing operations, means for introducing high-pressure air into a front chamber of the operating cylinder, disposed on the front side of the operating piston, at the time of the breaking operation, and an exhaust valve (which includes a valve element) operable in response to the air pressure within the front chamber of, the operating cylinder.
In the above described conventional operating device, when the high-pressure air is introduced into the front chamber at the time of the breaking operation, the exhaust valve is closed by the movement of the valve element, so that the air can not be discharged from the front chamber. It is not until after the operating piston moves a considerable distance from the time of start of the breaking operation that the exhaust port of the operating cylinder is communicated with a rear chamber of the operating cylinder disposed on the rear side of the operating piston. Therefore, as the operating piston moves, the air within the front chamber is not discharged, whereas, the air within the rear chamber is discharged therefrom via the exhaust port. Therefore, the operating piston can be moved at high speed to thereby carry out the breaking operation at high speed.
When the operating piston moves near the position where the breaking operation is completed, the exhaust port is isolated from the rear chamber, and is communicated with the front chamber, so that the high pressure air within the front chamber is discharged therefrom. When the pressure within the front chamber decreases below a predetermined level, the exhaust valve is opened by the movement of the valve element, so that the pressure within the front chamber is further decreased. Therefore, when the breaking operation is completed, the pressure within the front chamber is sufficiently low, and therefore the re-closing operation can be carried out in an extremely short time period after the completion of the breaking operation, and besides this closing operation can be effected at high speed.
As described above, the above conventional operating device for the gas circuit breaker is suited for carrying out the operation from the start of the breaking operation to the end of the re-closing operation at high speed. However, this operating device has the following disadvantages.
The exhaust valve is arranged in an eccentric relationship with respect to the axis (centerline) of a rod of the operating piston, and when the valve element is in the position to open the exhaust valve, a pressure-receiving portion, formed at the distal end of the valve element of the exhaust valve, is urged by a spring to be projected into the front chamber of the operating cylinder. When the closing operation is completed, the operating piston urges the pressure receiving portion of the valve element against the bias of the spring so as to move the valve element to the position to close the exhaust valve. Thereafter, until the high-pressure air is introduced into the front chamber, the valve element is held by the operating piston in the latter position. With this arrangement wherein the operating piston mechanically urges or pushes the pressure-receiving portion of the valve element, the reliability of the movement of the valve element may be lowered, and also this may cause damage to the sliding portion of the valve element. Since the operating piston of the eccentrically disposed exhaust valve strikes the pressure-receiving portion of the valve element of the exhaust valve, at a high speed, the pressure-receiving portion is subjected to an eccentric force and galling develops between the operating piston and the operating cylinder, so that contact sliding surfaces thereof may be damaged, and also this may adversely affect the smooth movement of the operating piston.